Sandy soils produce tobaccos with a thin leaf, curing to a yellow or bright red colour.
The claying system involved the expense of large curing houses and the employment of many hands, and forty days at least were required for completing the operation and making the sugar fit for the market, whereas with centrifugals sugar cooked to-day can go to market to-morrow, and the labour employed is reduced to a minimum.
When centrifugals were adopted for purging the whole crop (they had long been used for curing the second or third sugars), the system then obtaining of running the sugar into wagons or coolers, which was necessary for the second and third sugars' cooked only to string point, was continued, but latterly " crystallization in movement, a development of the system which forty years ago or more existed in refineries and in Cuba, has come into general use, and with great advantage, especially where proprietors have been able to erect appropriate buildings and machinery for carrying out the system efficiently.
Several grades are produced in Venezuela, determined by geographical position, altitude and method of curing and preparing for market.
This indefiniteness of images is sometimes said to be due to diffraction by the edge of the aperture, and proposals have even been made for curing it by causing the transition between the interrupted and transmitted parts of the primary wave to be less abrupt.